Anyone else have fond memories of this one? I played quite an interesting one shot using the Shadow Chaser setting framework.

For those that never played it, d20 Modern is...pretty much what it says on the tin, actually. The d20 system, applied to a modern setting. The core book had three setting frameworks, a few of which were expanded upon in a couple sourcebooks. The first of these was Shadow Chasers, which is your "monsters live in the shadows, and we protect the world from them" type of deal. Agents of Psi was espionage action with psionics. Urban Arcana was basically D&D if you viewed it through the lens of modern urban fantasy. There were also a few sourcebooks, a couple of which were finished but went unreleased after the cancellation of the line. d20 Future gave you sci-fi stuff and a few different possible futures and d20 Past gave you models for running games in different historical eras. Urban Arcana got its own sourcebook, expanding on the stuff presented in the core. d20 Apocalypse gives you a couple different post-apocalypse campaign models, Cyberscape (if I remember right) expanded on some of the swank cybernetic stuff in d20 Future, and then there's d20 Dark Matter, which ported over a setting called Dark Matter from another system.

I only ever played the one game of it, but oh boy did I enjoy the concepts a lot.